Um, I haven't touch this Blog for a while... So... just a case study.
Usually, I use FTP to find available files to update my mobile application. However,I have a client who doesn't want to install FTP but they have web server. Therefore, I use the traditional way to update the application, "Make a http query"... It is pretty simple to use HttpWebRequest and HttpWebResponse to validate the version. If the server returns a file link, then I download it and install it.



You can make a HttpWebRequest (http://yourwebsite/?version=1.0.2.0) to find available update. If server redirects you to a cab file, so we have an update.



Once user clicks "Yes", the we start to download and install the cab file.



Have a look the following example in C#. It handles downloading the cab file with progress bar. 

private void backgroundWorker1_DoWork(object sender, BCD.ComponentModel.DoWorkEventArgs e)
{
    HttpWebRequest myRequest = null;
    HttpWebResponse myResponse = null;
    string newurl = (string)e.Argument;
    string fileName = "", filePath = "";
    try
    {
        bool redirecting = true;

        while (redirecting)
        {
            try
            {
                myRequest = (HttpWebRequest)WebRequest.Create(newurl);
                // we accept any type of file
                myRequest.Accept = "*/*";
                // set the timeout to 5 seconds
                myRequest.Timeout = 5000;
                // casts the response
                myResponse = (HttpWebResponse)myRequest.GetResponse();
                // if we have redirection
                if ((int)myResponse.StatusCode == 301 || (int)myResponse.StatusCode == 302)
                {
                    string uriString = myResponse.Headers["Location"];
                    newurl = uriString;
                    // and keep going
                }
                else
                {
                    // gets the final uri
                    fileName = Path.GetFileName(myResponse.ResponseUri.LocalPath);
                    // we only want CAB file
                    if (fileName.ToLower().EndsWith(".cab"))
                    {
                        filePath = Path.Combine(Utils.TempPath, fileName);
                        // gets the total lenth for progress bar
                        long fileLength = myResponse.ContentLength;
                        // start with zero
                        int byteTotal = 0;
                        // start writing file
                        using (FileStream fileStream = File.OpenWrite(filePath))
                        {
                            // gets the stream from response object
                            using (Stream remoteStream = myResponse.GetResponseStream())
                            {
                                // we make 4 MB as our buffer
                                byte[] inBuffer = new byte[4 * 1024];

                                int nRead = remoteStream.Read(inBuffer, 0, 
                                    inBuffer.Length);

                                // we need to put e.Cancel as user may cancel downloading
                                while (nRead > 0 && !e.Cancel)
                                {
                                    if (nRead > 0)
                                        fileStream.Write(inBuffer, 0, nRead);

                                    byteTotal += nRead;
                                    // calculate the progress out of a base "100"
                                    double percentage = 
                                        (double)(byteTotal) / (double)fileLength;

                                    // update the progress
                                    backgroundWorker1.ReportProgress(
                                        (int)(percentage * 100));

                                    nRead = remoteStream.Read(inBuffer, 0, 
                                        inBuffer.Length);
                                }
                                myResponse.Close();
                                myRequest.Abort();
                            }
                        }

                        // if everything is fine
                        if (!e.Cancel)
                        {
                            // write the file time to be same as the original file time
                            BCD.IO.FileEx.SetCreationTime(filePath, 
                                myResponse.LastModified);
                            e.Result = filePath;
                        }
                        else
                        {
                            if (File.Exists(filePath))
                                File.Delete(filePath);
                        }
                    }
                    redirecting = false;
                }
            }
            catch (Exception ex)
            {
                redirecting = false;
                Utils.WriteToLog(ex);
            }
        }
    }
    catch (Exception ex)
    {
        // if error happens on retriving map, assign the error image instead
        Utils.WriteToLog(ex);
    }
    finally
    {
        if (myResponse != null)
            myResponse.Close();

        myRequest = null;
        myResponse = null;
    }
}